1. Field of the Invention
This invention relates to an image heating apparatus applied to an image forming apparatus such as a copier or a printer, and particularly to an apparatus in which a moving member slides relative to a supporting member.
2. Related Background Art
For the sake of convenience, an image heating apparatus (fixing apparatus) for heating and fixing a toner image on a recording material which is provided in an image forming apparatus such as a copier or a printer will hereinafter be described as an example.
In an image forming apparatus, an apparatus of the heat roller type has been widely used as a fixing apparatus for heating and fixing an unfixed image (toner image) of image information formed and borne on a recording material (such as a transferring material sheet, an electrofax sheet, electrostatic recording paper, an OHP sheet, printing paper or format paper) in a suitable image forming process means portion such as an electrophotographic process, an electrostatic recording process or a magnetic recording process by a transferring system or a direct system as a permanently secured image on the surface of the recording material.
Recently, from the viewpoints of quick start and energy saving, an apparatus of a film heating type using a heater has been put into practical use. An apparatus of a film heating type utilizing electromagnetic induction heating has also been proposed.
Fixing apparatuses of the film heating type using a heater have been proposed, for example, Japanese Patent Application Laid-Open No. 63-313182, Japanese Patent Application Laid-Open No. 2-157878, Japanese Patent Application Laid-Open No. 4-44075, Japanese Patent Application Laid-Open No. 4-204980, etc.
That is, heat-resisting film (fixing film or fixing belt) is sandwiched between a ceramic heater generally as a heating member and a pressurizing roller as a pressurizing member to thereby form a fixing nip portion, and a recording material on which an unfixed toner image to be fixed is formed and borne is introduced into between the fixing film and the pressurizing roller in the fixing nip portion and is sandwiched and conveyed with the fixing film, whereby in the fixing nip portion, the heat of the ceramic heater is given to the recording material through the fixing film, and the unfixed toner image is heat-and-pressure-fixed on the surface of the recording material by the pressure force of the fixing nip portion.
The fixing apparatus of this film heating type can use members of low heat capacity as the ceramic heater and the fixing film to constitute an apparatus of the on-demand type, and has the advantages that the ceramic heater as a heat source can be electrically energized to thereby generate heat to a predetermined fixing temperature only when the image forming apparatus executes image formation, that the waiting time from the closing of the power source switch of the image forming apparatus till a state in which image formation is executable is short (quick start property), and that the power consumption during standby is greatly small (power saving).
Japanese Patent Application Laid-Open No. 7-114276 proposes a heating apparatus in which an eddy current is created in fixing film itself or an electrically conductive member proximate to the fixing film and heat is generated by Joule heat. This film heating system utilizing electromagnetic induction permits a heat generating region to be proximate to a member to be heated and can therefore achieve the increased efficiency of consumed energy.
In a heating and fixing apparatus of the film heating type, as a method of driving cylindrical or endless fixing film as a rotary member, there is a method of rotating the fixing film brought into pressure contact by a film guide member (film supporting member) for guiding the inner peripheral surface of the fixing film and a pressurizing roller by the rotative driving of the pressurizing roller (a pressurizing roller driving system), or a method of stretching the endless fixing film by a driving roller and a tension roller provided in the endless fixing film, and driving the film.
In the apparatus of the film heating type, as proposed in Japanese Patent Application Laid-Open No. 5-27619, in order to mitigate the influence of rotational torque by the friction between the fixing film and the film guide member, a lubricant such as heat-resisting grease has been interposed between the inner surface of the fixing film and the film guide member to thereby secure the slidability between the fixing film and the film guide member.
As described above, in the heating and fixing apparatus of the film heating type, the inner surface of the fixing film and the film guide member slide in the fixing nip portion and therefore, heat-resisting grease has been applied to the surface of the sliding portion, but when the fixing film is rotated, the lubricant has been swept out from between the fixing film and the surface of the sliding portion by the pressure force for forming the fixing nip portion, and very little of the lubricant on the surface of the sliding portion corresponding to the fixing nip portion has been left.
Therefore, the close contact force between the fixing film and the surface of the sliding portion is increased by duration test when the room temperature or the like is low, and torque rises and thus, such an inconvenience as the fixing jam of recording materials has sometimes occurred due to the loss of synchronism of the driving roller (driving motor) and the slip of the driving roller relative to the fixing film.
It is an object of the present invention to provide an image heating apparatus improved in the slidability of a moving member and a supporting member.
It is another object of the present invention to provide an image heating apparatus having a supporting member, a moving member slidable with the supporting member, and a backup member forming a nip with the supporting member via the moving member, a lubricant being provided between the supporting member and the moving member, an image on a recording material being heated at the nip by heat from the moving member, the supporting member having a plurality of recess portions in a surface thereof adjacent to the moving member, a width of one of the plurality of recess portions in a moving direction of the moving member being smaller than a width of the nip in that direction, the plurality of recess portions being arranged in the moving direction of the moving member, and ranging over the whole of the nip in the moving direction of the moving member.
It is still another object of the present invention to provide an image heating apparatus having a supporting member, a moving member slidable with the supporting member, and a backup member forming a nip with the supporting member via the moving member, a lubricant being provided between the supporting member and the moving member, an image on a recording material being heated at the nip by the heat from the moving member, the supporting member having a plurality of recess portions in a surface thereof adjacent to the moving member, a width of one of the plurality of recess portions in a moving direction of the moving member being smaller than a width of the nip in that direction, the plurality of recess portions overlapping one another with respect to the moving direction of the moving member over a length of the nip in a direction orthogonal to the moving direction of the moving member.
It is yet still another object of the present invention to provide an image heating apparatus having a supporting member and a moving member slidable with the supporting member, a lubricant being provided between the supporting member and the moving member, an image on a recording material being heated by the heat from the moving member, the supporting member having a groove in a surface thereof adjacent to the moving member, an angle of the groove with respect to a direction orthogonal to the moving direction of the moving member being less than 45xc2x0.
It is a further object of the present invention to provide an image heating apparatus having a supporting member and a moving member movable with the supporting member, a lubricant being provided between the supporting member and the moving member, an image on a recording material being heated by heat from the moving member, the supporting member having a first groove and a second groove in a surface thereof adjacent to the moving member, the first groove and the second groove intersecting with each other.
Further objects of the present invention will become apparent from the following description.